JP7759010B2 - ventilation equipment - Google Patents

Description

Regarding ventilation equipment.

Patent Document 1 (JP 2023-051676 A) discloses a ventilation device equipped with a refrigerant circuit connecting a compressor, a first heat exchanger, and a second heat exchanger through which a refrigerant flows, an air supply fan that supplies outside air that has passed through the first heat exchanger indoors, and an exhaust fan that exhausts indoor air through the second heat exchanger. The ventilation device in Patent Document 1 uses the first heat exchanger to exchange heat between the supply air and heat recovered from the outside air by the second heat exchanger, thereby adjusting the temperature of the space to be ventilated.

The ventilation device disclosed in Patent Document 1 processes heat load using only two heat exchangers, which means there is a limit to the amount of heat load it can process, making it sometimes impossible to stably regulate the temperature.

This disclosure provides a ventilation device that can handle a greater heat load than conventional devices, allowing for stable temperature regulation.

A ventilation device of a first aspect ventilates air within a target space. The ventilation device includes a refrigerant circuit, a first fan, and a second fan. The refrigerant circuit is filled with refrigerant, and is connected to a compressor, a first heat exchanger, and a second heat exchanger. The first fan discharges outside air, which is air outside the target space, into the target space through the first heat exchanger. The second fan discharges air within the target space to outside the target space through the second heat exchanger. The refrigerant circuit is further connected to a third heat exchanger that exchanges heat between the refrigerant and a heat medium other than the refrigerant.

This ventilation system has a third heat exchanger connected to the refrigerant circuit that exchanges heat between the outside air and the refrigerant. By operating this third heat exchanger, the third heat exchanger can supplement the capacity of the second heat exchanger. This allows this ventilation system to handle a greater heat load than conventional systems and provide stable temperature control.

A ventilation device according to a second aspect is the ventilation device according to the first aspect, further comprising a flow path adjustment mechanism. The flow path adjustment mechanism adjusts the flow path of the refrigerant through the refrigerant circuit between a first state that restricts the flow of refrigerant into the third heat exchanger and a second state that allows the flow of refrigerant into the third heat exchanger.

With this ventilation device, the flow path adjustment mechanism can adjust the refrigerant flow path between a state in which refrigerant flows into the third heat exchanger and a state in which refrigerant does not flow into the third heat exchanger. As a result, this ventilation device can reduce power consumption compared to when the third heat exchanger is always functioning.

A ventilation device according to a third aspect is the ventilation device according to the second aspect, further comprising a control unit that controls the flow path adjustment mechanism. The control unit determines whether the refrigerant in the refrigerant circuit is in a first refrigerant state based on the pressure or temperature of the refrigerant in the refrigerant circuit, and if it determines that the refrigerant in the refrigerant circuit is in the first refrigerant state, sets the flow path adjustment mechanism to the second state, and if it determines that the refrigerant in the refrigerant circuit is not in the first refrigerant state, sets the flow path adjustment mechanism to the first state.

In ventilation systems that use the first heat exchanger to exchange heat between the supply air and the heat recovered from the outside air by the second heat exchanger, fluctuations in the outside air temperature and the room temperature can make it difficult for the first and second heat exchangers alone to handle the heat load, making it impossible to stably regulate the temperature.

When in the first refrigerant state, this ventilation device can have the third heat exchanger supplement the capacity of the first or second heat exchanger. Therefore, this ventilation device can perform stable temperature control even when the outside air temperature and indoor temperature fluctuate.

A ventilation device according to a fourth aspect is the ventilation device according to the third aspect, further comprising a third fan that blows air to the third heat exchanger. The control unit determines whether the refrigerant in the refrigerant circuit is in a first refrigerant state based on the pressure or temperature of the refrigerant in the refrigerant circuit. If the control unit determines that the refrigerant in the refrigerant circuit is in the first refrigerant state, it operates the third fan, and if the control unit determines that the refrigerant in the refrigerant circuit is not in the first refrigerant state, it stops the third fan.

When in the first refrigerant state, this ventilation device can cause the third heat exchanger to further supplement the capacity of the first or second heat exchanger. Therefore, this ventilation device can perform stable temperature control even when the outside air temperature and indoor temperature fluctuate.

A fifth aspect of the ventilation device is the ventilation device of any one of the first to fourth aspects, further comprising a third fan that blows air to the third heat exchanger. The third heat exchanger, the third fan, and the compressor are housed in a single housing.

With this ventilation device, the third heat exchanger, third fan, and compressor are housed in a single housing, minimizing the amount of space required for installation.

A sixth aspect of the ventilation device is a ventilation device according to any one of the first to fifth aspects, in which the third heat exchanger is installed outside the target space.

If the third heat exchanger is installed inside the target space, a duct is required to send outside air to the third heat exchanger. With this ventilation device, the third heat exchanger is installed outside the target space, eliminating the need to install a duct, thereby preventing the ventilation device's structure from becoming too complex.

A seventh aspect of the ventilation device is a ventilation device according to any one of the first to fifth aspects, wherein the ventilation device includes a plurality of first units each having a first heat exchanger and a first fan, and a plurality of second units each having a second heat exchanger and a second fan.

This ventilation device can ventilate multiple target spaces.

The ventilation device of an eighth aspect is the ventilation device of any one of the first to seventh aspects, in which the heat medium is outside air.

A ninth aspect of the ventilation device is a ventilation device according to any one of the first to eighth aspects, wherein the third heat exchanger functions as an evaporator when the second heat exchanger functions as an evaporator, and functions as a condenser when the second heat exchanger functions as a condenser.

1 is a schematic configuration diagram of a ventilation device 1 according to a first embodiment. FIG. 2 is a refrigerant circuit diagram of the ventilation device 1. FIG. 7 is a block diagram that schematically illustrates a control unit 700 and each unit connected to the control unit 700. 10 is a flowchart showing a processing flow executed by a control unit 700. FIG. 10 is a refrigerant circuit diagram before the third heat exchanger is in a functional state. FIG. 10 is a refrigerant circuit diagram during the third heat exchanger function state. FIG. 10 is a refrigerant circuit diagram of the third heat exchanger in a functional state when the first four-way switching valve 371 is in the second state. FIG. 10 is a refrigerant circuit diagram of a compressor unit 300a of a ventilation device 1a according to a second embodiment. 3 is a refrigerant circuit diagram of the air supply unit 100, the exhaust unit 200, and the flow path switching unit 600a of the ventilation device 1a. FIG. FIG. 2 is a block diagram schematically illustrating a control unit 700a and each unit connected to the control unit 700a. FIG. 10 is a refrigerant circuit diagram before the third heat exchanger is in a functional state. FIG. 10 is a refrigerant circuit diagram before the third heat exchanger is in a functional state. FIG. 10 is a refrigerant circuit diagram during the third heat exchanger function state. FIG. 10 is a refrigerant circuit diagram in a third heat exchanger functional state when the four-way switching valve 370a is in the second state.

First Embodiment
(1) Overall Configuration Fig. 1 is a schematic configuration diagram of a ventilation device 1 according to a first embodiment. Fig. 2 is a refrigerant circuit diagram of the ventilation device 1.

Ventilation device 1 is installed in a building such as a building or factory, and ventilates the air within target spaces Sa, Sb, and Sc, which are ventilation target spaces included in the building. Ventilation device 1 includes air supply units 100a, 100b, and 100c, exhaust units 200a, 200b, and 200c, a compressor unit 300, a flow path switching unit 600, and a control unit 700.

The air supply unit 100a and the exhaust unit 200a form one pair 400a and ventilate the target space Sa. The air supply unit 100b and the exhaust unit 200b form one pair 400b and ventilate the target space Sb. The air supply unit 100c and the exhaust unit 200c form one pair 400c and ventilate the target space Sc.

Air supply units 100a, 100b, and 100c are structurally identical except for the target spaces Sa, Sb, and Sc to be ventilated. Therefore, hereinafter, when describing features common to air supply units 100a, 100b, and 100c, they will be referred to as "air supply unit 100" without the reference symbols "a," "b," and "c." Similarly, exhaust units 200a, 200b, and 200c are structurally identical except for the target spaces Sa, Sb, and Sc to be ventilated. Therefore, hereinafter, when describing features common to exhaust units 200a, 200b, and 200c, they will be referred to as "exhaust unit 200" without the reference symbols "a," "b," and "c." Furthermore, when describing features common to pairs 400a, 400b, and 400c, they will be referred to as "pair 400" without the reference symbols "a," "b," and "c."

As shown in FIG. 2, the air supply unit 100, exhaust unit 200, compressor unit 300, and flow path switching unit 600 are connected via a liquid refrigerant connection pipe 510, a high-pressure gas refrigerant connection pipe 520, and a low-pressure gas refrigerant connection pipe 530 to form a refrigerant circuit 500. The refrigerant circuit 500 is filled with refrigerant. The refrigerant filled in the refrigerant circuit 500 circulates within the refrigerant circuit 500 as the compressor 330, described below, operates. The ventilation device 1 operates as a vapor compression refrigeration cycle by circulating the refrigerant within the refrigerant circuit 500.

Detailed operation will be described later, but the ventilation operation performed by the ventilation device 1 includes a temperature control operation in which each of the pairs 400 controls the temperature of the supply air SA. The temperature control operation includes a cooling operation and a heating operation. In the cooling operation, the supply air unit 100 cools the supply air SA using heat recovered by the exhaust unit 200 from the return air RA. In the heating operation, the supply air unit 100 heats the supply air SA using heat recovered by the exhaust unit 200 from the return air RA. The ventilation device 1 can perform cooling operation and heating operation individually for each of the pairs 400.

Furthermore, when the refrigerant in the refrigerant circuit 500 is in the first refrigerant state (described below) during temperature adjustment operation, the ventilation device 1 activates the third heat exchanger 310 (described below). At this time, the third heat exchanger 310 supplements the heat exchange capacity of the second heat exchanger 210.

(2) Detailed Configuration (2-1) Air Supply Unit 100
The air supply unit 100 has a first heat exchanger 110, a first fan 120, a first flow rate adjustment valve 130, and a sensor 140. The first heat exchanger 110, the first fan 120, the first flow rate adjustment valve 130, and the sensor 140 are housed in a first housing 101. The air supply unit 100 is an example of a first unit.

The air supply unit 100 is installed on the wall surrounding the target space S.

(2-1-1) First heat exchanger 110
The first heat exchanger 110 exchanges heat between the refrigerant flowing through the first heat exchanger 110 and the supply air SA.

The first end 110a of the first heat exchanger 110 is connected to the first main liquid refrigerant pipe 611 (described below) of the first liquid refrigerant pipe 610. The second end 110b of the first heat exchanger 110 is connected to the first combined gas refrigerant pipe 623 (described below) of the first gas refrigerant pipe 620.

(2-1-2) First fan 120
The first fan 120 discharges the outside air OA as supply air SA into the target space S through the first heat exchanger 110. The rotation speed of the first fan 120 is controlled by the control unit 700.

(2-1-3) First flow rate control valve 130
The first flow rate control valve 130 adjusts the flow rate of the refrigerant in the first main liquid refrigerant pipe 611. The first flow rate control valve 130 is provided at the first end 110a of the first heat exchanger 110.

The opening degree of the first flow rate adjustment valve 130 is controlled by the control unit 700.

(2-1-4) Sensor 140
The sensor 140 includes an outside air temperature sensor 141. The outside air temperature sensor 141 is, for example, a thermistor.

The outside air temperature sensor 141 detects the temperature To of the outside air OA. The outside air temperature sensor 141 is positioned in the air flow before it passes through the first heat exchanger 110.

Sensor 140 may further include a supply air temperature sensor, a liquid-side refrigerant temperature sensor, and a gas-side refrigerant temperature sensor (all not shown). At least one of the supply air temperature sensor, the liquid-side refrigerant temperature sensor, and the gas-side refrigerant temperature sensor is, for example, a thermistor.

The supply air temperature sensor is positioned in the air flow after passing through the first heat exchanger 110 and detects the temperature Ts of the supply air SA.

The liquid-side refrigerant temperature sensor is positioned at the first end 110a of the first heat exchanger 110 and detects the temperature of the refrigerant passing through the first end 110a of the first heat exchanger 110.

The gas side refrigerant temperature sensor is positioned at the second end 110b of the first heat exchanger 110 and detects the temperature of the refrigerant passing through the second end 110b of the first heat exchanger 110.

(2-2) Exhaust unit 200
The exhaust unit 200 has a second heat exchanger 210, a second fan 220, a second flow rate adjustment valve 230, and a sensor 240. The second heat exchanger 210, the second fan 220, the second flow rate adjustment valve 230, and the sensor 240 are housed in a second housing 201. The exhaust unit 200 is an example of a second unit.

The exhaust unit 200 is installed on the wall surrounding the target space S.

(2-2-1) Second heat exchanger 210
The second heat exchanger 210 exchanges heat between the refrigerant flowing through the second heat exchanger 210 and the return air RA.

The first end 210a of the second heat exchanger 210 is connected to the second main liquid refrigerant pipe 641 (described below) of the second liquid refrigerant pipe 640. The second end 210b of the second heat exchanger 210 is connected to the second junction gas refrigerant pipe 653 (described below) of the second gas refrigerant pipe 650.

(2-2-2) Second fan 220
The second fan 220 discharges the return air RA as exhaust air EA to the outside of the target space S through the second heat exchanger 210. The rotation speed of the second fan 220 is controlled by the control unit 700.

(2-2-3) Second flow rate control valve 230
The second flow rate control valve 230 adjusts the flow rate of the refrigerant in the second main liquid refrigerant pipe 231. The second flow rate control valve 230 is provided at the first end 210a of the second heat exchanger 210.

The opening degree of the second flow rate control valve 230 is controlled by the control unit 700.

(2-2-4) Sensor 240
The sensors 240 include a carbon dioxide concentration sensor 241 and a return air temperature sensor 242. The return air temperature sensor 242 is a thermistor.

The carbon dioxide concentration sensor 241 detects the concentration of carbon dioxide contained in the return air RA. The carbon dioxide concentration sensor 241 is positioned in the air flow before passing through the second heat exchanger 210.

The return air temperature sensor 242 detects the temperature Tr of the return air RA. The return air temperature sensor 242 is positioned in the air flow before it passes through the second heat exchanger 210.

The sensor 240 may further include a liquid-side refrigerant temperature sensor 243 and a gas-side refrigerant temperature sensor 244 (both not shown). At least one of the liquid-side refrigerant temperature sensor 243 and the gas-side refrigerant temperature sensor 244 is, for example, a thermistor.

The liquid-side refrigerant temperature sensor is positioned at the first end 210a of the second heat exchanger 210 and detects the temperature of the refrigerant passing through the first end 210a of the second heat exchanger 210.

The gas side refrigerant temperature sensor is positioned at the second end 210b of the second heat exchanger 210 and detects the temperature of the refrigerant passing through the second end 210b of the second heat exchanger 210.

(2-3) Compressor unit 300
The compressor unit 300 includes a third heat exchanger 310, a third fan 320, a compressor 330, a connecting pipe 340, a check valve 350, a third control valve 360, a four-way switching valve 370, and a sensor 380. The third heat exchanger 310, the third fan 320, the compressor 330, the connecting pipe 340, the check valve 350, the third control valve 360, the four-way switching valve 370, and the sensor 380 are housed in a third housing 301.

The compressor unit 300 is installed outside the target space S (e.g., outside the building, in the attic space of the building, etc.).

(2-3-1) Third heat exchanger 310
The third heat exchanger 310 exchanges heat between the refrigerant flowing through the third heat exchanger 310 and the outside air OA. The outside air OA that has passed through the third heat exchanger 310 is discharged outside the target space S. Since the compressor unit 300 is installed outside the target space S, the third heat exchanger 310 is also installed outside the target space S.

The first end 311a of the third heat exchanger 310 is connected to the first four-way switching valve 371 (described below) of the four-way switching valve 370. The second end 311b of the third heat exchanger 310 is connected to the liquid refrigerant communication pipe 510 via the third connection pipe 343.

(2-3-2) Third fan 320
The third fan 320 blows the outside air OA to the third heat exchanger 310. The rotation speed of the third fan 320 is controlled by the control unit 700.

(2-3-3) Compressor 330
The compressor 330 draws low-pressure refrigerant in the refrigerant circuit 500 through a suction pipe 331 , compresses it to a predetermined pressure, and then discharges it from a discharge pipe 332 as high-pressure refrigerant.

The suction pipe 331 is connected to the low-pressure gas refrigerant connection pipe 530.

The discharge pipe 332 is connected to the first four-way switching valve 371 (described below) of the four-way switching valve 370.

The operating capacity of compressor 330 is controlled by control unit 700. Compressor 330 is a compressor whose operating capacity can be changed, for example, by inverter-controlling the compressor motor.

(2-3-4) Connection pipe 340
The connection pipe 340 includes a first connection pipe 341 , a second connection pipe 342 , and a third connection pipe 343 .

One end of the first connection pipe 341 is connected to the second four-way switching valve 372 (described below) of the four-way switching valve 370, and the other end is connected to the high-pressure gas refrigerant communication pipe 520.

One end of the second connection pipe 342 is connected to the first four-way switching valve 371, and the other end is connected to the low-pressure gas refrigerant communication pipe 530 and the suction pipe 331.

The third connection pipe 343 is connected to the second end 311b of the third heat exchanger 310, and the other end is connected to the liquid refrigerant connection pipe 510.

(2-3-5) Check valve 350
The check valve 350 prevents refrigerant from flowing from the discharge pipe 332 into the compressor 330. The check valve 350 is provided in a portion of the discharge pipe 332 closer to the compressor 330 than the portion where the discharge pipe 332 is connected to the third port 372c of the second four-way switching valve 372.

(2-3-6) Third control valve 360
The third control valve 360 adjusts the flow path of the refrigerant flowing through the refrigerant circuit 500 between a closed state that restricts the inflow of refrigerant into the third heat exchanger 310 and an open state that allows the inflow of refrigerant into the third heat exchanger 310. The third control valve 360 controls the flow of refrigerant in the third connecting pipe 343. The third control valve 360 is provided in the third connecting pipe 343.

The third control valve 360 is controlled between an open state and a closed state by the control unit 700.

The third control valve 360 is an example of a flow path adjustment mechanism. The closed state is an example of a first state, and the open state is an example of a second state.

(2-3-7) Four-way switching valve 370
The four-way switching valve 370 includes a first four-way switching valve 371 and a second four-way switching valve 372. As shown in Fig. 2, the first four-way switching valve 371 and the second four-way switching valve 372 block the flow of refrigerant in one port, and effectively function as a three-way valve.

The first four-way switching valve 371 changes between a first state and a second state to switch the refrigerant flow path. The first four-way switching valve 371 has a first port 371a, a second port 371b, and a third port 371c. The first port 371a is connected to the discharge pipe 332 of the compressor 330. The second port 371b is connected to the first end 311a of the third heat exchanger 310. The third port 371c is connected to the low-pressure gas refrigerant communication pipe 530 via the second connection pipe 342.

In the first state, the first four-way switching valve 371 connects the first port 371a to the second port 371b (see the solid line of the first four-way switching valve 371 in Figure 2), and in the second state, connects the second port 371b to the third port 371c (see the dotted line of the first four-way switching valve 371 in Figure 2). The first four-way switching valve 371 is controlled by the control unit 700.

The second four-way switching valve 372 changes between a first state and a second state to switch the refrigerant flow path. The second four-way switching valve 372 has a first port 372a, a second port 372b, and a third port 372c. The first port 372a is connected to the suction pipe 331 of the compressor 330. The second port 372b is connected to the low-pressure gas refrigerant communication pipe 530 via the second connection pipe 342. The third port 372c is connected to the discharge pipe 332 of the compressor 330.

In the first state, the second four-way switching valve 372 connects the second port 372b to the third port 372c (see the solid line of the second four-way switching valve 372 in Figure 2), and in the second state, connects the first port 372a to the second port 372b (see the dotted line of the second four-way switching valve 372 in Figure 2). The second four-way switching valve 372 is controlled by the control unit 700.

(2-3-8) Sensor 380
The sensors 380 include an intake pressure sensor 381 and a discharge pressure sensor 382 .

The suction pressure sensor 381 detects the suction pressure Ps of the refrigerant in the suction pipe 331. The suction pressure sensor 381 is located in the suction pipe 331.

The discharge pressure sensor 382 detects the discharge pressure Pd of the refrigerant in the discharge pipe 332. The discharge pressure sensor 382 is arranged in the discharge pipe 332.

Sensor 380 may further include an intake air temperature sensor, a discharge air temperature sensor, a liquid-side refrigerant temperature sensor, and a gas-side refrigerant temperature sensor (all not shown). At least one of the intake air temperature sensor, the discharge air temperature sensor, the liquid-side refrigerant temperature sensor, and the gas-side refrigerant temperature sensor is, for example, a thermistor.

The intake air temperature sensor detects the temperature of the air drawn in by the third fan 320. The intake air temperature sensor is positioned in the air flow before it passes through the third heat exchanger 310.

The discharge air temperature sensor detects the temperature of the air that passes through the third heat exchanger 310 and is discharged. The discharge air temperature sensor is positioned in the air flow after passing through the third heat exchanger 310.

The gas side refrigerant temperature sensor detects the temperature of the refrigerant passing through the first end 311a of the third heat exchanger 310. The gas side refrigerant temperature sensor is positioned at the first end 311a of the third heat exchanger 310.

The liquid-side refrigerant temperature sensor detects the temperature of the refrigerant passing through the second end 311b of the third heat exchanger 310. The liquid-side refrigerant temperature sensor is positioned at the second end 311b of the third heat exchanger 310.

(2-4) Flow path switching unit 600
The flow path switching unit 600 switches the flow path of the refrigerant flowing through the refrigerant circuit 500. The flow path switching unit 600 has a first liquid refrigerant pipe 610, a first gas refrigerant pipe 620, a first control valve 630, a second liquid refrigerant pipe 640, a second gas refrigerant pipe 650, and a second control valve 660.

The first liquid refrigerant pipe 610, the first gas refrigerant pipe 620, the first control valve 630, the second liquid refrigerant pipe 640, the second gas refrigerant pipe 650, and the second control valve 660 are housed in the fourth housing 601.

As shown in FIG. 2, the flow path switching unit 600 has at least the same number of pairs 400 as the first gas refrigerant pipe 620, first control valve 630, second liquid refrigerant pipe 640, second gas refrigerant pipe 650, and second control valve 660.

(2-4-1) First liquid refrigerant pipe 610
The first liquid refrigerant pipe 610 connects the liquid refrigerant communication pipe 510 and the air supply unit 100. The first liquid refrigerant pipe 610 has one end connected to the liquid refrigerant communication pipe 510 and the other end connected to the first end 110a of the first heat exchanger 110.

(2-4-2) First gas refrigerant pipe 620
The first gas refrigerant piping 620 connects the high-pressure gas refrigerant communication pipe 520 and the low-pressure gas refrigerant communication pipe 530 to the air supply unit 100. The first gas refrigerant piping 620 includes a first high/low pressure gas refrigerant piping 621, a first low-pressure gas refrigerant piping 622, and a first junction gas refrigerant piping 623.

One end of the first high/low pressure gas refrigerant pipe 621 is connected to the high pressure gas refrigerant connection pipe 520, and the other end is connected to the first combined gas refrigerant pipe 623.

One end of the first low-pressure gas refrigerant pipe 622 is connected to the low-pressure gas refrigerant communication pipe 530, and the other end is connected to the first combined gas refrigerant pipe 623.

The first combined gas refrigerant pipe 623 is connected at one end to the first high- and low-pressure gas refrigerant pipe 621 and the first low-pressure gas refrigerant pipe 622, and at the other end to the second end 110b of the first heat exchanger 110.

(2-4-3) First control valve 630
The first control valve 630 controls the flow of refrigerant in the first gas refrigerant pipe 620. The first control valve 630 includes a first high-pressure gas refrigerant control valve 631 and a first low-pressure gas refrigerant control valve 632.

The first high-pressure gas refrigerant control valve 631 is provided in the first high-low pressure gas refrigerant piping 621 and controls the refrigerant flowing through the first high-low pressure gas refrigerant piping 621.

The first low-pressure gas refrigerant control valve 632 is provided in the first low-pressure gas refrigerant piping 622 and controls the refrigerant flowing through the first low-pressure gas refrigerant piping 622.

The first high-pressure gas refrigerant control valve 631 and the first low-pressure gas refrigerant control valve 632 are controlled by the control unit 700 between an open state and a closed state.

(2-4-4) Second liquid refrigerant pipe 640
The second liquid refrigerant pipe 640 connects the liquid refrigerant communication pipe 510 and the exhaust unit 200. The second liquid refrigerant pipe 640 has one end connected to the liquid refrigerant communication pipe 510 and the other end connected to the first end 210a of the second heat exchanger 210.

(2-4-5) Second gas refrigerant pipe 650
The second gas refrigerant piping 650 connects the high-pressure gas refrigerant communication pipe 520 and the low-pressure gas refrigerant communication pipe 530 to the exhaust unit 200. The second gas refrigerant piping 650 includes a second high/low pressure gas refrigerant piping 651, a second low-pressure gas refrigerant piping 652, and a second combined gas refrigerant piping 653.

The second high/low pressure gas refrigerant pipe 651 is connected at one end to the high pressure gas refrigerant connection pipe 520 and at the other end to the second combined gas refrigerant pipe 653.

One end of the second low-pressure gas refrigerant pipe 652 is connected to the low-pressure gas refrigerant communication pipe 530, and the other end is connected to the second combined gas refrigerant pipe 653.

The second combined gas refrigerant pipe 653 is connected at one end to the second high/low pressure gas refrigerant pipe 651 and the second low pressure gas refrigerant pipe 652, and at the other end to the second end 210b of the second heat exchanger 210.

(2-4-6) Second control valve 660
The second control valve 660 controls the flow of refrigerant in the second gas refrigerant pipe 650. The second control valve 660 includes a second high-pressure gas refrigerant control valve 661 and a second low-pressure gas refrigerant control valve 662.

The second high-pressure gas refrigerant control valve 661 is provided in the second high-low pressure gas refrigerant piping 651 and controls the refrigerant flowing through the second high-low pressure gas refrigerant piping 651.

The second low-pressure gas refrigerant control valve 662 is provided in the second low-pressure gas refrigerant piping 652 and controls the refrigerant flowing through the second low-pressure gas refrigerant piping 652.

The second high-pressure gas refrigerant control valve 661 and the second low-pressure gas refrigerant control valve 662 are controlled by the control unit 700 between an open state and a closed state.

(2-5) Control Unit 700
The control unit 700 is electrically connected to the first fan 120, the first flow rate control valve 130, the sensor 140, the second fan 220, the second flow rate control valve 230, the sensor 240, the third fan 320, the compressor 330, the third control valve 360, the four-way switching valve 370 (the first four-way switching valve 371 and the second four-way switching valve 372), the sensor 380, the first control valve 630 (the first high-pressure gas refrigerant control valve 631 and the first low-pressure gas refrigerant control valve 632), and the second control valve 660 (the second high-pressure gas refrigerant control valve 661 and the second low-pressure gas refrigerant control valve 662) so as to be able to send and receive control signals and the like. The control unit 700 is housed in the third housing 301.

The user can operate the control unit 700 via a controller such as a remote control (also referred to as a management terminal, etc.; not shown). For example, the user can set the set temperature Tse of the target space S via the remote control. This causes the set temperature Tse to be recorded in a storage device (described below) of the control unit 700. A remote control may be provided for each pair 400.

Figure 3 is a block diagram that shows the control unit 700 and each unit connected to the control unit 700.

The control unit 700 controls the third control valve 360 between a closed state and an open state. More specifically, the control unit 700 determines whether the refrigerant in the refrigerant circuit 500 is in a first refrigerant state based on the pressure or temperature of the refrigerant in the refrigerant circuit 500. If the control unit 700 determines that the refrigerant in the refrigerant circuit 500 is in the first refrigerant state, it opens the third control valve 360. If the control unit 700 determines that the refrigerant in the refrigerant circuit 500 is not in the first refrigerant state, it closes the third control valve 360. The closed state is an example of the first state, and the open state is an example of the second state.

The control unit 700 may also control the third control valve 360 and the third fan 320 based on a determination of whether the refrigerant is in the first refrigerant state. Specifically, the control unit 700 may determine whether the refrigerant in the refrigerant circuit 500 is in the first refrigerant state based on the pressure or temperature of the refrigerant in the refrigerant circuit 500, and may operate the third fan 320 if it determines that the refrigerant in the refrigerant circuit 500 is in the first refrigerant state, and may stop the third fan 320 if it determines that the refrigerant in the refrigerant circuit 500 is not in the first refrigerant state.

The control unit 700 is realized by a computer. The control unit 700 includes a control and arithmetic unit and a storage device (neither of which are shown). The control and arithmetic unit is a processor such as a CPU or GPU. The control and arithmetic unit reads a program stored in the storage device and performs predetermined processing in accordance with this program. Furthermore, the control and arithmetic unit writes the results of calculations to the storage device and reads information stored in the storage device in accordance with the program.

(3) Operation of the Ventilation Device 1 (3-1) Processing Flow Executed by the Control Unit 700 FIG. 4 is a flowchart showing the processing flow executed by the control unit 700.

When the power (not shown) of the ventilation device 1 is turned on, the control unit 700 begins executing the following processing flow.

In step S100, the control unit 700 begins controlling the rotation speeds of the first fan 120 and the second fan 220.

In the rotation speed control, the control unit 700 controls the rotation speed of the first fan 120 and the second fan 220 for each of the target spaces Sa, Sb, and Sc based on the carbon dioxide concentration D detected by the carbon dioxide concentration sensor 241. The control unit 700 may also control the rotation speed of the first fan 120 and the second fan 220 for each pair 400 according to the fan rotation speed step (fan tap) selected by a user or the like.

In step S110, the control unit 700 determines whether or not to perform temperature control operation for each of pairs 400a, 400b, and 400c. If the control unit 700 determines that temperature control operation will be performed for at least one pair 400 (Yes), the process proceeds to step S120. If the control unit 700 determines that temperature control operation will not be performed for all pairs 400 (No), the process proceeds to step S110. In other words, the control unit 700 repeats step S110 until it determines that temperature control operation will be performed for at least one pair 400.

Temperature control operation includes cooling operation and heating operation. Whether cooling operation or heating operation is performed during temperature control operation can be set for each pair 400. Whether cooling operation or heating operation is performed during temperature control operation may be set by the user, or may be set by the control unit 700 based on conditions such as the temperature To of the outside air OA.

The control unit 700 determines whether to perform temperature control operation based on the temperature To of the outside air OA and the temperature Tr of the return air RA.

Specifically, when the pair 400 is set to perform cooling operation, the control unit 700 first acquires and compares the set temperature Tse set by the user using the remote control and the temperature To detected by the outside air temperature sensor 141. If the temperature To is higher than the set temperature Tse, the control unit 700 determines to perform cooling operation, and if the temperature To is equal to or lower than the temperature Ts, the control unit 700 determines not to perform cooling operation.

The control unit 700 acquires and compares the temperature To detected by the outside air temperature sensor 141 and the temperature Tr detected by the return air temperature sensor 242. The control unit 700 may then determine to perform cooling operation if temperature To is higher than temperature Tr, and may determine not to perform cooling operation if temperature To is equal to or lower than temperature Tr.

When the pair 400 is set to perform heating operation, the control unit 700 first acquires and compares the set temperature Tse set by the user using the remote control and the temperature To detected by the outside air temperature sensor 141. If the temperature To is lower than the set temperature Tse, the control unit 700 determines to perform heating operation, and if the temperature To is equal to or higher than the temperature Ts, the control unit 700 determines not to perform heating operation.

The control unit 700 acquires and compares the temperature To detected by the outside air temperature sensor 141 and the temperature Tr detected by the return air temperature sensor 242. The control unit 700 then determines to perform heating operation if the temperature To is lower than the temperature Tr, and determines not to perform heating operation if the temperature To is equal to or higher than the temperature Tr.

In step S120, the control unit 700 stops control of the rotation speeds of the first fan 120 and the second fan 220 for the pair 400 for which it has determined that temperature adjustment operation should be performed, then starts temperature adjustment operation (specifically, cooling operation or heating operation), and proceeds to step S130. Details of cooling operation and heating operation will be described later.

In step S130, the control unit 700 determines whether the refrigerant in the refrigerant circuit 500 is in the first refrigerant state based on the pressure or temperature of the refrigerant in the refrigerant circuit 500.

If the control unit 700 determines that the refrigerant in the refrigerant circuit 500 is in the first refrigerant state (Yes), the process proceeds to step S140. If the control unit 700 determines that the refrigerant in the refrigerant circuit 500 is not in the first refrigerant state (No), the process proceeds to step S130. In other words, the control unit 700 repeats step S130 until it determines that the refrigerant in the refrigerant circuit 500 is in the first refrigerant state.

The first refrigerant state occurs when it is necessary to assist the thermal load of the first heat exchanger 110 or the thermal load of the second heat exchanger 210. The control unit 700 determines that the refrigerant in the refrigerant circuit 500 is in the first refrigerant state when the evaporation temperature Te of the refrigerant is lower than a predetermined temperature Tt1.

The evaporation temperature Te is obtained by converting the suction pressure Ps detected by the suction pressure sensor 381 into the saturation temperature of the refrigerant.

In step S140, the control unit 700 places the refrigerant circuit 500 in a state in which the third heat exchanger 310 is functional (hereinafter referred to as the "third heat exchanger functional state"), and proceeds to step S150.

Details of the third heat exchanger functional state will be discussed later.

In step S150, the control unit 700 determines whether or not to terminate the third heat exchanger function state. If the control unit 700 determines that the third heat exchanger function state should be terminated (Yes), the process proceeds to step S160. If the control unit 700 determines that the third heat exchanger function state should not be terminated (No), the process proceeds to step S150. In other words, the control unit 700 repeats step S150 until it determines that the third heat exchanger function state should be terminated.

The control unit 700 determines whether to terminate the third heat exchanger function state based on the pressure or temperature of the refrigerant in the refrigerant circuit 500. Specifically, the control unit 700 determines to switch the third control valve 360 from an open state to a closed state when the refrigerant evaporation temperature Te is higher than a predetermined temperature Tt2.

The predetermined temperature Tt2 is set to a value that is expected to prevent the refrigerant in the refrigerant circuit 500 from entering the first refrigerant state even after the third heat exchanger function state is terminated.

In step S160, the control unit 700 terminates the third heat exchanger function state and proceeds to step S170.

In step S170, the control unit 700 determines whether or not to terminate the temperature adjustment operation for the pair 400 for which the temperature adjustment operation is being performed. If the control unit 700 determines that the temperature adjustment operation should be terminated (Yes), the process proceeds to step S180. If the control unit 700 determines that the temperature adjustment operation should not be terminated (No), the process proceeds to step S170. In other words, the control unit 700 repeats step S170 until it determines that the temperature adjustment operation should be terminated.

When pair 400 is performing cooling operation, the control unit 700 determines to terminate the cooling operation, which is a temperature control operation, if temperature To is equal to or lower than set temperature Tse, and determines not to terminate the cooling operation if temperature To is higher than set temperature Tse.

When pair 400 is performing heating operation, the control unit 700 determines to terminate the heating operation, which is a temperature adjustment operation, if temperature To is equal to or higher than the set temperature Tse, and determines not to terminate the heating operation if temperature To is lower than the set temperature Tse.

In step S180, the control unit 700 ends the temperature adjustment operation and proceeds to step S100.

The control unit 700 will terminate execution of this processing flow if the power to the ventilation device 1 is turned off, regardless of which step is being executed.

(3-2) Temperature Control Operation Figure 5 is a refrigerant circuit diagram before the third heat exchanger function state. Figure 6 is a refrigerant circuit diagram during the third heat exchanger function state. In Figures 5 and 6, the direction of refrigerant flow is indicated by arrows. Figure 5 shows, as an example, a ventilator 1 in which pairs 400a and 400c perform heating operation and pair 400b performs cooling operation.

(3-2-1) Compressor unit 300
When the control unit 700 starts the temperature adjustment operation, it starts the compressor 330, closes the third control valve 360, sets the first four-way switching valve 371 to the first state, and sets the second four-way switching valve 372 to the first state. At this time, the control unit 700 does not start (operate) the third fan 320.

As a result, the compressor 330 draws refrigerant in the low-pressure gas refrigerant communication pipe 530 through the suction pipe 331 and discharges it as high-pressure refrigerant from the discharge pipe 332. The refrigerant compressed to high pressure by the compressor 330 passes through the discharge pipe 332, the check valve 350, the third port 372c of the second four-way switching valve 372, and the second port 372b of the second four-way switching valve 372, in that order, before flowing into the high-pressure gas refrigerant communication pipe 520. At this time, because the third control valve 360 is closed, the flow of refrigerant into the third heat exchanger 310 is restricted.

The control unit 700 controls the rotation speed of the compressor 330 so that appropriate operating conditions are achieved based on the measurement values of the sensors 140, 240, 380, the set temperature, etc. (for example, so that one or more of the evaporation temperature, condensation temperature, degree of subcooling, degree of superheat, etc., reach the target value).

(3-2-2) Flow path switching unit 600 and pair 400 of air supply unit 100 and exhaust unit 200 performing cooling operation
For the pair 400 determined to perform cooling operation (pair 400b in FIG. 5 ), the control unit 700 closes the corresponding first high-pressure gas refrigerant control valve 631, opens the corresponding first low-pressure gas refrigerant control valve 632, opens the corresponding second high-pressure gas refrigerant control valve 661, and closes the corresponding second low-pressure gas refrigerant control valve 662. Additionally, the control unit 700 controls the rotation speeds of the first fan 120 and the second fan 220 and adjusts the apertures of the first flow rate control valve 130 and the second flow rate control valve 230 so that appropriate operating conditions are achieved based on the measurement values of the sensors 140, 240, 380, the set temperature, and the like (for example, so that one or more of the evaporation temperature, condensation temperature, degree of subcooling, degree of superheat, etc., reach target values).

As a result, the high-pressure refrigerant flowing through the high-pressure gas refrigerant communication pipe 520 passes through the second high/low pressure gas refrigerant pipe 651, the second combined gas refrigerant pipe 653, the second heat exchanger 210, and the second liquid refrigerant pipe 640 in that order, before flowing into the liquid refrigerant communication pipe 510. At this time, the flow rate of the refrigerant passing through the second liquid refrigerant pipe 640 is regulated by the second flow control valve 230.

The refrigerant that flows into the liquid refrigerant connection pipe 510 passes through the first liquid refrigerant pipe 610, the first heat exchanger 110, the first combined gas refrigerant pipe 623, and the first low-pressure gas refrigerant pipe 622 in that order, before flowing into the low-pressure gas refrigerant connection pipe 530. At this time, the flow rate of the refrigerant passing through the first liquid refrigerant pipe 610 is regulated by the first flow control valve 130.

By flowing the refrigerant in this manner, the first heat exchanger 110 functions as a refrigerant evaporator, and the second heat exchanger 210 functions as a refrigerant condenser. As a result, the air supply unit 100 cools the supply air SA blown by the first fan 120 in the first heat exchanger 110 and then releases it into the target space S. In addition, the exhaust unit 200 heats the return air RA blown by the second fan 220 in the second heat exchanger 210 and then releases it outside the target space S as exhaust air EA. Heating the return air RA by the exhaust unit 200 corresponds to heat recovery from the return air RA.

(3-2-3) Flow path switching unit 600 and pair 400 of air supply unit 100 and exhaust unit 200 performing heating operation
For the pair 400 for which it has determined that heating operation should be performed (pair 400a and pair 400c in FIG. 5 ), the control unit 700 opens the corresponding first high-pressure gas refrigerant control valve 631, closes the corresponding first low-pressure gas refrigerant control valve 632, closes the corresponding second high-pressure gas refrigerant control valve 661, and opens the corresponding second low-pressure gas refrigerant control valve 662. Additionally, the control unit 700 controls the rotation speeds of the first fan 120 and the second fan 220 and adjusts the apertures of the first flow rate control valve 130 and the second flow rate control valve 230 so that appropriate operating conditions are achieved based on the measurement values of the sensors 140, 240, 380, the set temperature, and the like (for example, so that one or more of the evaporation temperature, condensation temperature, degree of subcooling, degree of superheat, etc., reach target values).

As a result, the high-pressure refrigerant flowing through the high-pressure gas refrigerant communication pipe 520 passes through the first high/low pressure gas refrigerant pipe 621, the first combined gas refrigerant pipe 623, the first heat exchanger 110, and the first liquid refrigerant pipe 610, in that order, before flowing into the liquid refrigerant communication pipe 510. At this time, the flow rate of the refrigerant passing through the first liquid refrigerant pipe 610 is regulated by the first flow control valve 130.

The refrigerant that flows into the liquid refrigerant connection pipe 510 passes through the second liquid refrigerant pipe 640, the second heat exchanger 210, the second combined gas refrigerant pipe 653, and the second low-pressure gas refrigerant pipe 652 in that order, before flowing into the low-pressure gas refrigerant connection pipe 530. At this time, the flow rate of the refrigerant passing through the second liquid refrigerant pipe 640 is regulated by the second flow control valve 230.

By flowing the refrigerant in this manner, the first heat exchanger 110 functions as a refrigerant condenser, and the second heat exchanger 210 functions as a refrigerant evaporator. As a result, the air supply unit 100 heats the supply air SA blown by the first fan 120 in the first heat exchanger 110 and then releases it into the target space S. In addition, the exhaust unit 200 cools the return air RA blown by the second fan 220 in the second heat exchanger 210 and then releases it outside the target space S as exhaust air EA. The cooling of the return air RA by the exhaust unit 200 corresponds to heat recovery from the return air RA.

(3-2-4) Pair 400 of air supply unit 100 and exhaust unit 200 that does not perform temperature adjustment operation
Although not shown in the figure, for pairs 400 for which the control unit 700 has determined that temperature adjustment operation will not be performed, the first high-pressure gas refrigerant control valve 631, the first low-pressure gas refrigerant control valve 632, the second high-pressure gas refrigerant control valve 661, and the second low-pressure gas refrigerant control valve 662 are all closed.

This restricts the refrigerant flowing through the liquid refrigerant connection pipe 510, the high-pressure gas refrigerant connection pipe 520, and the low-pressure gas refrigerant connection pipe 530 from flowing into the air supply unit 100 and the exhaust unit 200. As a result, the first heat exchanger 110 and the second heat exchanger 210 are restricted from functioning as heat exchangers.

(3-2-5) Compressor unit 300 in the third heat exchanger function state
When the control unit 700 determines that the refrigerant circuit 500 is to be in the third heat exchanger function state, it switches the closed third control valve 360 to an open state and operates the stopped third fan 320 to start speed control. When the third control valve 360 is opened, a portion of the refrigerant flowing through the discharge pipe 332 passes through the first port 371a of the first four-way switching valve 371, the second port 371b of the first four-way switching valve 371, the third heat exchanger 310, and the third control valve 360 in that order, and then flows into the liquid refrigerant connection pipe 510. At this time, the control unit 700 starts speed control of the third fan 320 so that appropriate operating conditions are achieved (e.g., so that one or more of the evaporation temperature, condensation temperature, degree of subcooling, degree of superheat, etc., reach target values) based on the measurement values of the sensors 140, 240, 380, the set temperature, etc.

By allowing the refrigerant to flow in this manner, the third heat exchanger 310 functions as a refrigerant condenser. As a result, even if fluctuations in the outside air OA and return air RA cause an increase in the heat load of the first heat exchanger 110, which functions as an evaporator, the third heat exchanger 310 compensates for the capacity of the second heat exchanger 210, which functions as a condenser. Therefore, the ventilator 1 can perform stable temperature regulation.

(4) Modification (4-1) 1A
The control unit 700 may set the refrigerant circuit 500 in the third heat exchanger function state when the first four-way switching valve 371 is in the second state. Fig. 7 is a refrigerant circuit diagram in the third heat exchanger function state when the first four-way switching valve 371 is in the second state.

In this case, when the third control valve 360 is opened, the compressor 330 draws refrigerant from the liquid refrigerant communication pipe 510 through the third control valve 360, the third heat exchanger 310, the second port 371b of the first four-way switching valve 371, the third port 371c of the first four-way switching valve 371, and the second connecting pipe 342 into the suction pipe 331, and discharges it as high-pressure refrigerant from the discharge pipe 332. Thereafter, the refrigerant discharged from the compressor 330 flows through the refrigerant circuit 500 as in the first embodiment, and therefore detailed description will be omitted.

By allowing the refrigerant to flow in this manner, the third heat exchanger 310 functions as an evaporator for the refrigerant. As a result, even if fluctuations in the outside air OA and return air RA cause an increase in the heat load on the first heat exchanger 110, which functions as a condenser, the third heat exchanger 310 compensates for the capacity of the second heat exchanger 210, which functions as an evaporator. Therefore, the ventilator 1 can perform stable temperature regulation.

(4-2) Modification 1B
The number of pairs 400 may be one, two, or four or more. Furthermore, a plurality of pairs 400 may ventilate one target space S. Furthermore, the number of air supply units 100 and exhaust units 200 that ventilate one target space S do not have to be the same.

When there is one pair 400, the control unit 700 causes the third heat exchanger 310 to function as an evaporator when the second heat exchanger 210 functions as an evaporator, and causes the third heat exchanger 310 to function as a condenser when the second heat exchanger 210 functions as a condenser.

(4-3) Modification 1C
The first heat exchanger 110, the first fan 120, the first flow rate control valve 130, and the sensor 140 of the air supply unit 100 do not have to be housed in a single housing. For example, the first heat exchanger 110 and the first fan 120 may be installed in a location such as a machine room away from the treatment space, separately from other equipment, via a duct or the like.

Similarly, the second heat exchanger 210, second fan 220, second flow rate control valve 230, and sensor 240 of the exhaust unit 200 do not have to be housed in a single housing. The third heat exchanger 310, third fan 320, compressor 330, connecting piping 340, check valve 350, third control valve 360, four-way switching valve 370, and sensor 380 of the compressor unit 300 do not have to be housed in a single housing. The first liquid refrigerant piping 610, first gas refrigerant piping 620, first control valve 630, second liquid refrigerant piping 640, second gas refrigerant piping 650, and second control valve 660 of the flow path switching unit 600 do not have to be housed in a single housing.

(4-4) Modification 1D
The control unit 700 may be realized by a plurality of control units provided individually for each of the air supply unit 100, the exhaust unit 200, the flow path switching unit 600, and the compressor unit 300. In this case, the respective control units may be electrically connected to each other so as to be able to send and receive control signals, etc., and may cooperate with each other to realize each operation. Also, any one of the electrically connected control units may collectively control the other control units.

(4-5) Modification 1E
The control unit 700 may be realized by a server that provides cloud computing services and is connected to the air supply unit 100, the exhaust unit 200, the flow path switching unit 600, and the compressor unit 300 via a network.

(4-6) Modification 1F
The heat medium with which the refrigerant exchanges heat in the third heat exchanger 310 is not limited to the air outside the building. For example, the heat medium with which the refrigerant exchanges heat in the third heat exchanger 310 may be the air of a room in which the pair 400 is not installed (in other words, a room other than the target space S).

In addition, in the third heat exchanger 310, the heat medium with which the refrigerant exchanges heat may be water flowing through a water circuit (not shown). In this case, the third heat exchanger 310 has a refrigerant flow path connected to the refrigerant circuit 500 and a water flow path connected to the water circuit, and heat is exchanged between the refrigerant flowing through the refrigerant flow path and the water flowing through the water flow path.

(4-7) Modification 1G
The ventilation device 1 may be capable of performing an operation for only ventilation without recovering heat. For example, the ventilation device 1 may perform only ventilation of the target space S without recovering heat by controlling the first fan 120 and the second fan 220 without starting the compressor 330.

(4-8) Modification 1H
In addition to the case where it is necessary to assist the thermal load of the first heat exchanger 110 or the thermal load of the second heat exchanger 210, the control unit 700 may also put the refrigerant circuit 500 into the third heat exchanger function state in the following cases.

The control unit 700 may place the refrigerant circuit 500 in the third heat exchanger function state when the refrigerant pressure may exceed the design pressure of the refrigerant circuit 500. In this case, the control unit 700 places the refrigerant circuit 500 in the third heat exchanger function state when the discharge pressure Pd is higher than the predetermined pressure Pt1.

The control unit 700 may place the refrigerant circuit 500 in the third heat exchanger function state even if the refrigerant in the refrigerant circuit 500 is not in the first refrigerant state if it determines that the capacity of the first heat exchanger 110 and the second heat exchanger 210 is insufficient. In this case, the control unit 700 acquires the temperature of the refrigerant passing through the first end 210a of the second heat exchanger 210 detected by the liquid-side refrigerant temperature sensor for the pair 400 performing cooling operation, and acquires the temperature of the refrigerant passing through the second end 210b of the second heat exchanger 210 detected by the gas-side refrigerant temperature sensor for the pair 400 performing heating operation. The control unit 700 then determines whether to place the refrigerant circuit 500 in the third heat exchanger function state based on the difference between the acquired temperature and a predetermined temperature (which may be the same or different between cooling operation and heating operation).

The control unit 700 may place the refrigerant circuit 500 in the third heat exchanger function state when the load on the compressor 330 increases and there is a risk that the temperature of the sliding parts (not shown) inside the compressor 330 will exceed the allowable value. In this case, the control unit 700 places the refrigerant circuit 500 in the third heat exchanger function state when the condensation temperature Tc of the refrigerant is higher than a predetermined temperature Tt3. The condensation temperature Tc is obtained by converting the discharge pressure Pd detected by the discharge pressure sensor 382 into the saturation temperature of the refrigerant.

The control unit 700 may place the refrigerant circuit 500 in the third heat exchanger function state when there is a risk of condensation water freezing on the surface of the second heat exchanger 210 in any of the pairs 400. In this case, the control unit 700 places the refrigerant circuit 500 in the third heat exchanger function state when the suction pressure Ps in any of the pairs 400 is lower than a predetermined pressure, or when the temperature of the refrigerant passing through the first end 210a of the second heat exchanger 210 detected by the liquid-side refrigerant temperature sensor is lower than a predetermined temperature.

(4-9) Modification 1I
The control unit 700 may determine whether to put the refrigerant circuit 500 into the third heat exchanger function state based on the pressure or temperature of the refrigerant in the refrigerant circuit 500, taking into account not only whether the refrigerant in the refrigerant circuit 500 is in the first refrigerant state but also the power consumption of the compressor 330 and the power consumption of the third fan 320.

Specifically, after determining that the refrigerant in the refrigerant circuit 500 is in the first refrigerant state based on the pressure or temperature of the refrigerant in the refrigerant circuit 500 (if S130 returns "Yes"), the control unit 700 determines whether the power consumption Pw1 of the third fan 320, which increases when the refrigerant circuit 500 is in the third heat exchanger function state, exceeds the current power consumption Pw2 of the compressor 330 when the refrigerant circuit 500 is not in the third heat exchanger function state. If the power consumption Pw1 exceeds the power consumption Pw2, the control unit 700 determines that the refrigerant circuit 500 is in the third heat exchanger function state.

This prevents the overall power consumption of the ventilation device 1 from increasing as a result of starting the third fan 320 to operate the third heat exchanger 310.

(4-10) Modification 1J
In the ventilation device 1, the regulation of the inflow of refrigerant into the third heat exchanger 310 (in other words, the flow path regulation mechanism) is realized by the third control valve 360, but the regulation of the inflow of refrigerant into the third heat exchanger 310 may also be realized using a four-way switching valve and/or a control valve.

For example, a bypass valve may be provided that bypasses the third connecting pipe 343 and the first end 311a of the third heat exchanger 310. In this case, when the refrigerant in the refrigerant circuit 500 is in the first refrigerant state, the bypass valve, which is in a first state that does not bypass the third connecting pipe 343 and the first end 311a, is set to a second state that bypasses the third connecting pipe 343 and the first end 311a.

(5) Features (5-1)
The ventilation device 1 ventilates the air in a target space S. The ventilation device 1 includes a refrigerant circuit 500, a first fan 120, and a second fan 220. The refrigerant circuit 500 is connected to a compressor 330, a first heat exchanger 110, and a second heat exchanger 210, and is filled with refrigerant. The first fan 120 discharges outside air OA, which is air outside the target space S, into the target space S through the first heat exchanger 110. The second fan 220 discharges air within the target space S to outside the target space S through the second heat exchanger 210. The refrigerant circuit 500 is further connected to a third heat exchanger 310 that exchanges heat between the refrigerant and a heat medium other than the refrigerant (e.g., the outside air OA).

In the ventilation device 1, the third heat exchanger 310, which exchanges heat between the refrigerant and a heat medium other than the refrigerant, is connected to the refrigerant circuit 500. By operating the third heat exchanger 310, the third heat exchanger 310 can supplement the capacity of the second heat exchanger 210. This allows the ventilation device 1 to handle a greater heat load than conventional devices and provide stable temperature regulation.

(5-2)
The ventilation device 1 further includes a third control valve 360 (flow path adjustment mechanism). The third control valve 360 adjusts the flow path of the refrigerant flowing through the refrigerant circuit 500 between a closed state (first state) that restricts the inflow of refrigerant into the third heat exchanger 310 and an open state (second state) that allows the inflow of refrigerant into the third heat exchanger 310.

With the ventilation device 1, the third control valve 360 can adjust the refrigerant flow path between a state in which refrigerant flows into the third heat exchanger 310 and a state in which refrigerant does not flow into the third heat exchanger 310. Therefore, with the ventilation device 1, power consumption can be reduced compared to when the third heat exchanger 310 is constantly functioning.

(5-3)
The ventilation device 1 further includes a control unit 700 that controls the third control valve 360. The control unit 700 determines whether the refrigerant in the refrigerant circuit 500 is in the first refrigerant state based on the pressure or temperature of the refrigerant in the refrigerant circuit 500, and if it determines that the refrigerant in the refrigerant circuit 500 is in the first refrigerant state, it closes the third control valve 360, and if it determines that the refrigerant in the refrigerant circuit 500 is not in the first refrigerant state, it opens the third control valve 360.

In ventilation systems that use the first heat exchanger to exchange heat between the supply air and the heat recovered from the outside air by the second heat exchanger, fluctuations in the outside air temperature and the room temperature can make it difficult for the first and second heat exchangers alone to handle the heat load, making it impossible to stably regulate the temperature.

When the ventilation device 1 is in the first refrigerant state, the third heat exchanger 310 can supplement the capacity of the first heat exchanger 110 or the second heat exchanger 210. Therefore, the ventilation device 1 can perform stable temperature regulation even when the outside air temperature and indoor temperature fluctuate.

(5-4)
The ventilation device 1 further includes a third fan 320 that sends air to the third heat exchanger 310. The control unit 700 determines whether the refrigerant in the refrigerant circuit 500 is in the first refrigerant state based on the pressure or temperature of the refrigerant in the refrigerant circuit 500, and operates the third fan 320 when it determines that the refrigerant in the refrigerant circuit 500 is in the first refrigerant state, and stops the third fan 320 when it determines that the refrigerant in the refrigerant circuit 500 is not in the first refrigerant state.

When the ventilation device 1 is in the first refrigerant state, the third heat exchanger 310 can further supplement the capacity of the first heat exchanger 110 or the second heat exchanger 210. Therefore, the ventilation device 1 can perform stable temperature regulation even when the outside air temperature and indoor temperature fluctuate.

(5-5)
The ventilation device 1 further includes a third fan 320 that sends air to the third heat exchanger 310 .

The third heat exchanger 310, third fan 320, and compressor 330 are housed in a single third housing 301.

The third heat exchanger 310, third fan 320, and compressor 330 are housed in a single third housing 301, which prevents the installation space for the ventilation device 1 from becoming too large.

(5-6)
The third heat exchanger 310 is installed outside the target space S.

If the third heat exchanger 310 is installed within the target space S, a duct is required to send outside air OA to the third heat exchanger 310. By installing the third heat exchanger 310 outside the target space S, the installation of a duct is unnecessary, which prevents the structure of the ventilation device 1 from becoming too complex.

(5-7)
The ventilation device 1 includes a plurality of air supply units 100 (first units) each having a first heat exchanger 110 and a first fan 120, and a plurality of exhaust units 200 (second units) each having a second heat exchanger 210 and a second fan 220.

The ventilation device 1 can ventilate multiple target spaces. Furthermore, when ventilating multiple target spaces, the ventilation device 1 can install a pair 400 of an air supply unit 100 and an exhaust unit 200 for each target space. Therefore, the ventilation device 1 prevents the duct length from becoming too long compared to when a ventilation device in which an air supply heat exchanger, air supply fan, exhaust heat exchanger, and exhaust fan are housed in a single unit is connected to multiple target spaces via ducts. Furthermore, the ventilation device 1 can vary the heat exchange capacity of each pair 400.

(5-8)
The heat medium other than the refrigerant is outside air OA.

(5-9)
The third heat exchanger 310 functions as an evaporator when the second heat exchanger 210 functions as an evaporator, and functions as a condenser when the second heat exchanger 210 functions as a condenser.

Second Embodiment
(1) Overall Configuration Next, a ventilation device 1a according to a second embodiment will be described. The following description will focus on the differences between the ventilation device 1 and the ventilation device 1a, and descriptions of identical or corresponding features and well-known technologies may be omitted. Fig. 8A is a refrigerant circuit diagram of a compressor unit 300a of the ventilation device 1a according to the second embodiment. Fig. 8B is a refrigerant circuit diagram of the air supply unit 100, exhaust unit 200, and flow path switching unit 600a of the ventilation device 1a.

The main differences between ventilation device 1 and ventilation device 1a are that ventilation device 1a has a compressor unit 300a instead of compressor unit 300, a flow path switching unit 600a instead of flow path switching unit 600, and a low-pressure refrigerant communication pipe 540 and a high-pressure refrigerant communication pipe 550 that connect compressor unit 300a and flow path switching unit 600a to form a refrigerant circuit 500a.

(2) Detailed Configuration (2-1) Compressor Unit 300a
The compressor unit 300a includes a third heat exchanger 310a, a third fan 320, a compressor 330a, a connecting pipe 340a, a check valve 350a, a third control valve 360a, a fourth control valve 390, a four-way switching valve 370a, and a sensor 380.

(2-1-1) Third heat exchanger 310a
The third heat exchanger 310a exchanges heat between the refrigerant flowing through the third heat exchanger 310 and the outside air OA. Since the compressor unit 300 is installed outside the target space S, the third heat exchanger 310a is also installed outside the target space S.

The third heat exchanger 310a is provided so as to bypass the second connecting pipe 342a. The first end 311aa of the third heat exchanger 310a is connected to the four-way switching valve 370a side of the second connecting pipe 342a. The second end 311ab of the third heat exchanger 310a is connected to the high-pressure refrigerant communication pipe 550 side of the second connecting pipe 342a.

(2-1-2) Compressor 330a
The intake pipe 331 of the compressor 330a is connected to a third port 370ac (described later) of the four-way selector valve 370a.

The discharge pipe 332 of the compressor 330a is connected to the second port 370ab (described below) of the four-way switching valve 370a.

(2-1-3) Connection pipe 340a
The connection pipe 340a includes a first connection pipe 341a, a second connection pipe 342a, a third connection pipe 343a, and a fourth connection pipe 344a.

One end of the first connection pipe 341a is connected to the first port 370aa (described below) of the four-way switching valve 370a, and the other end is connected to the low-pressure refrigerant connection pipe 540.

One end of the second connection pipe 342a is connected to the fourth port 370ad (described below) of the four-way switching valve 370a, and the other end is connected to the high-pressure refrigerant connection pipe 550.

One end of the third connection pipe 343a is connected to the first connection pipe 341a between the four-way switching valve 370a and the first check valve 351a (described below), and the other end is connected to the second connection pipe 342a between the second check valve 352a (described below) and the high-pressure refrigerant communication pipe 550.

The fourth connection pipe 344a has one end connected to the first connection pipe 341a between the low-pressure refrigerant communication pipe 540 and the first check valve 351a, and the other end connected to the second connection pipe 342a between the second check valve 352a (described below) and the high-pressure refrigerant communication pipe 550.

(2-1-4) Check valve 350a
The check valve 350a includes a first check valve 351a, a second check valve 352a, a third check valve 353a, and a fourth check valve 354a. As shown in Fig. 7, the first check valve 351a, the second check valve 352a, the third check valve 353a, and the fourth check valve 354a are arranged to form a bridge.

The first check valve 351a is provided in the first connection pipe 341a. The first check valve 351a allows refrigerant to flow from the low-pressure refrigerant communication pipe 540 to the four-way switching valve 370a, and regulates the flow of refrigerant from the four-way switching valve 370a to the low-pressure refrigerant communication pipe 540.

The second check valve 352a is provided in the second connection pipe 342a. The second check valve 532a allows refrigerant to flow from the four-way switching valve 370a to the high-pressure refrigerant communication pipe 550 and restricts refrigerant flow from the high-pressure refrigerant communication pipe 550 to the four-way switching valve 370a.

The third check valve 353a is provided in the third connection pipe 343a. The third check valve 353a allows refrigerant to flow from the first connection pipe 341a to the second connection pipe 342a, and regulates the flow of refrigerant from the second connection pipe 342a to the first connection pipe 341a.

The fourth check valve 354a is provided in the fourth connection pipe 344a. The fourth check valve 354a allows refrigerant to flow from the first connection pipe 341a to the second connection pipe 342a, and restricts refrigerant from the second connection pipe 342a to the first connection pipe 341a.

(2-1-5) Third control valve 360a
The third control valve 360a controls the flow of refrigerant into the third heat exchanger 310a. The third control valve 360a is provided at a first end 311aa of the third heat exchanger 310a.

The third control valve 360a is controlled between an open state and a closed state by the control unit 700.

(2-1-6) Fourth control valve 390
The fourth control valve 390 controls the flow of refrigerant in the second connecting pipe 342a. The fourth control valve 390 is provided on the second connecting pipe 342a between a connecting portion with the first end 311aa of the third heat exchanger 310a and a connecting portion with the second end 310ab of the third heat exchanger 310a.

The fourth control valve 390 is controlled between an open state and a closed state by the control unit 700.

The fourth control valve 390, together with the third control valve 360a, constitutes an example of a flow path adjustment mechanism.

(2-1-7) Four-way switching valve 370a
The four-way switching valve 370a changes between a first state and a second state to switch the refrigerant flow path. The four-way switching valve 370a has a first port 370aa, a second port 370ab, a third port 370ac, and a fourth port 370ad. The first port 370aa is connected to the first connection pipe 341a. The second port 370ab is connected to the discharge pipe 332 of the compressor 330. The third port 370ac is connected to the suction pipe 331 of the compressor 330. The third port 370ac is connected to the first connection pipe 342b.

In a first state, the four-way switching valve 370a communicates between the first port 370aa and the third port 370ac, and between the second port 370ab and the fourth port 370ad (see the solid lines of the four-way switching valve 370a in Figure 8A). In a second state, the four-way switching valve 370a communicates between the first port 370aa and the second port 370ab, and between the third port 370ac and the fourth port 370ad (see the dotted lines of the four-way switching valve 370a in Figure 8A). The four-way switching valve 370a is controlled by the control unit 700a.

(2-2) Flow path switching unit 600a
The flow path switching unit 600a switches the flow path of the refrigerant flowing through the refrigerant circuit 500a. The flow path switching unit 600a has a first liquid refrigerant pipe 610a, a first gas refrigerant pipe 620a, a first control valve 630a, a second liquid refrigerant pipe 640a, a second gas refrigerant pipe 650a, a second control valve 660a, a gas-liquid separator 670, and a third flow rate adjustment valve 680.

The first liquid refrigerant pipe 610a, the first gas refrigerant pipe 620a, the first control valve 630a, the second liquid refrigerant pipe 640a, the second gas refrigerant pipe 650a, the second control valve 660a, and the gas-liquid separator 670 are housed in a housing (not shown).

(2-2-1) First liquid refrigerant pipe 610a
The first liquid refrigerant pipe 610a connects a liquid refrigerant outlet port 670c (described later) of the gas-liquid separator 670 to the air supply unit 100. One end of the first liquid refrigerant pipe 610a is connected to the liquid refrigerant outlet port 670c, and the other end is connected to the first end 110a of the first heat exchanger 110.

(2-2-2) First gas refrigerant pipe 620a
The first gas refrigerant pipe 620a connects the low-pressure refrigerant communication pipe 540 and a gas refrigerant outflow port 670b (described later) of the gas-liquid separator 670 to the air supply unit 100. The first gas refrigerant pipe 620a includes a first high/low pressure gas refrigerant pipe 621a, a first low-pressure gas refrigerant pipe 622a, and a first junction gas refrigerant pipe 623a.

One end of the first high/low pressure gas refrigerant pipe 621a is connected to the gas refrigerant outflow port 670b, and the other end is connected to the first combined gas refrigerant pipe 623a.

One end of the first low-pressure gas refrigerant pipe 622a is connected to the low-pressure refrigerant connection pipe 540, and the other end is connected to the first combined gas refrigerant pipe 623a.

The first combined gas refrigerant pipe 623a is connected at one end to the first high- and low-pressure gas refrigerant pipe 621a and the first low-pressure gas refrigerant pipe 622a, and at the other end to the second end 110b of the first heat exchanger 110.

(2-2-3) First control valve 630a
The first control valve 630a controls the flow of refrigerant in the first liquid refrigerant pipe 610a or the first gas refrigerant pipe 620a. The first control valve 630a includes a first high-pressure gas refrigerant control valve 631a and a first low-pressure gas refrigerant control valve 632a.

The first high-pressure gas refrigerant control valve 631a is provided in the first high-low pressure gas refrigerant piping 621a and controls the refrigerant flowing through the first high-low pressure gas refrigerant piping 621a.

The first low-pressure gas refrigerant control valve 632a is provided in the first low-pressure gas refrigerant piping 622a and controls the refrigerant flowing through the first low-pressure gas refrigerant piping 622a.

The first high-pressure gas refrigerant control valve 631 and the first low-pressure gas refrigerant control valve 632 are controlled by the control unit 700 between an open state and a closed state.

(2-2-4) Second liquid refrigerant pipe 640a
The second liquid refrigerant pipe 640a connects the liquid refrigerant outlet port 670c of the gas-liquid separator 670 to the exhaust unit 200. One end of the second liquid refrigerant pipe 640 is connected to the liquid refrigerant outlet port 670c, and the other end is connected to the first end 210a of the second heat exchanger 210.

(2-2-5) Second gas refrigerant pipe 650a
The second gas refrigerant pipe 650a connects the low-pressure refrigerant communication pipe 540 and the gas refrigerant outflow port 670b of the gas-liquid separator 670 to the exhaust unit 200. The second gas refrigerant pipe 650a includes a second high/low pressure gas refrigerant pipe 651a, a second low-pressure gas refrigerant pipe 652a, and a second junction gas refrigerant pipe 653a.

One end of the second high/low pressure gas refrigerant pipe 651a is connected to the gas refrigerant outflow port 670b, and the other end is connected to the second combined gas refrigerant pipe 653a.

One end of the second low-pressure gas refrigerant pipe 652a is connected to the low-pressure refrigerant connection pipe 540, and the other end is connected to the second combined gas refrigerant pipe 653a.

The second combined gas refrigerant pipe 653a is connected at one end to the second high- and low-pressure gas refrigerant pipe 651a and the second low-pressure gas refrigerant pipe 652a, and at the other end to the second end 210b of the second heat exchanger 210.

(2-2-6) Second control valve 660a
The second control valve 660a controls the flow of refrigerant in the second liquid refrigerant pipe 640a or the second gas refrigerant pipe 650. The second control valve 660a includes a second high-pressure gas refrigerant control valve 661a, a second low-pressure gas refrigerant control valve 662a, and a second liquid refrigerant control valve 663a.

The second high-pressure gas refrigerant control valve 661a is provided in the second high-low pressure gas refrigerant piping 651a and controls the refrigerant flowing through the second high-low pressure gas refrigerant piping 651a.

The second low-pressure gas refrigerant control valve 662a is provided in the second low-pressure gas refrigerant piping 652a and controls the refrigerant flowing through the second low-pressure gas refrigerant piping 652a.

The second liquid refrigerant control valve 663a is provided in the second liquid refrigerant piping 640a and controls the refrigerant flowing through the second liquid refrigerant piping 640a.

The second high-pressure gas refrigerant control valve 661a, the second low-pressure gas refrigerant control valve 662a, and the second liquid refrigerant control valve 663a are controlled between an open state and a closed state by the control unit 700.

(2-2-7) Gas-liquid separator 670
The gas-liquid separator 670 separates the refrigerant that flows in from the high-pressure refrigerant communication pipe 550 into liquid refrigerant and gas refrigerant. The gas-liquid separator 670 has a refrigerant inlet port 670a, a gas refrigerant outlet port 670b, and a liquid refrigerant outlet port 670c.

The refrigerant inlet port 670a is connected to the high-pressure refrigerant connection pipe 550. The gas refrigerant outlet port 670b is connected to the first high/low pressure gas refrigerant pipe 621a. The liquid refrigerant outlet port 670c is connected to the first liquid refrigerant pipe 610a.

(2-2-8) Third flow control valve 680
The third flow rate control valve 680 adjusts the flow rate of the refrigerant between the first liquid refrigerant pipe 610 and the gas-liquid separator 670. The third flow rate control valve 680 is provided on the refrigerant pipe connecting the first liquid refrigerant pipe 610 and the gas-liquid separator 670.

The opening degree of the third flow rate adjustment valve 680 is controlled by the control unit 700a.

(2-3) Control unit 700a
The control unit 700a is electrically connected to the first fan 120, the first flow rate control valve 130, the sensor 140, the second fan 220, the second flow rate control valve 230, the sensor 240, the third fan 320, the compressor 330a, the third control valve 360a, the fourth control valve 390, the four-way switching valve 370a, the sensor 380, the first control valve 630a (the first high-pressure gas refrigerant control valve 631a and the first low-pressure gas refrigerant control valve 632a), the second control valve 660a (the second high-pressure gas refrigerant control valve 661a and the second low-pressure gas refrigerant control valve 662a), and the third flow rate control valve 680 so as to be able to send and receive control signals and the like.

Figure 9 is a block diagram that shows the control unit 700a and the components connected to the control unit 700a.

(3) Operation of the Ventilation Device 1a (3-1) Temperature Control Operation Figures 10A and 10B are refrigerant circuit diagrams before the third heat exchanger function state. Figure 11 is a refrigerant circuit diagram during the third heat exchanger function state. In Figures 10A, 10B, and 11, the direction of refrigerant flow is indicated by arrows. Figure 10B shows, as an example, a ventilation device 1 in which pairs 400a and 400c perform heating operation and pair 400b performs cooling operation.

Note that the refrigerant flow in the air supply unit 100, exhaust unit 200, and flow path switching unit 600a in the third heat exchanger functional state is the same as that shown in Figure 10B, and therefore will not be described here.

(3-1-1) Compressor unit 300a
When the control unit 700a starts the temperature adjustment operation, it starts the compressor 330a, closes the third control valve 360a, opens the fourth control valve 390a, and sets the four-way switching valve 370a to the first state. At this time, the control unit 700 does not start the third fan 320.

As a result, the compressor 330a draws refrigerant from the low-pressure refrigerant communication pipe 540 through the first check valve 351a, the first port 370aa of the four-way switching valve 370a, and the third port 370ac of the four-way switching valve 370a into the suction pipe 331a, and discharges it as high-pressure refrigerant from the discharge pipe 332a. The refrigerant compressed to high pressure by the compressor 330a passes through the discharge pipe 332a, the second port 370ab of the four-way switching valve 370a, the fourth port 370ad of the four-way switching valve 370a, the fourth control valve 390, and the second check valve 352b, in that order, before flowing into the high-pressure refrigerant communication pipe 550. At this time, because the third control valve 360a is closed, the flow of refrigerant into the third heat exchanger 310 is restricted.

The control unit 700a controls the rotation speed of the compressor 330a so that appropriate operating conditions are achieved based on the measurement values of the sensors 140, 240, 380, the set temperature, etc. (for example, so that one or more of the evaporation temperature, condensation temperature, degree of subcooling, degree of superheat, etc., reach the target value).

(3-1-2) Flow path switching unit 600a and pair 400 of air supply unit 100 and exhaust unit 200 performing cooling operation
For the pair 400 for which the control unit 700a has determined to perform cooling operation (pair 400b in FIG. 10B ), the control unit 700a closes the corresponding first high-pressure gas refrigerant control valve 631a, opens the corresponding first low-pressure gas refrigerant control valve 632a, opens the corresponding second high-pressure gas refrigerant control valve 661a, and closes the corresponding second low-pressure gas refrigerant control valve 662a. The control unit 700a also controls the rotation speeds of the first fan 120 and the second fan 220 and adjusts the apertures of the first flow rate control valve 130, the second flow rate control valve 230, and the third flow rate control valve 680 so that appropriate operating conditions are achieved (for example, so that one or more of the evaporation temperature, condensation temperature, degree of subcooling, degree of superheat, etc., reach target values) based on the measurement values of the sensors 140, 240, 380, the set temperature, and the like.

As a result, the refrigerant that flows from the high-pressure refrigerant communication pipe 550 into the gas-liquid separator 670 passes through the gas refrigerant outflow port 670b, the second high- and low-pressure gas refrigerant pipe 651a, the second merging gas refrigerant pipe 653a, the second heat exchanger 210, and the second liquid refrigerant pipe 640a, in that order. At this time, the flow rate of the refrigerant passing through the second liquid refrigerant pipe 640a is regulated by the second flow control valve 230.

The refrigerant flowing out from the second liquid refrigerant pipe 640a, together with the refrigerant flowing out from the liquid refrigerant outlet port 670c of the gas-liquid separator 670, passes through the first liquid refrigerant pipe 610a, the first heat exchanger 110, the first combined gas refrigerant pipe 623a, and the first low-pressure gas refrigerant pipe 622a, in that order, before flowing into the low-pressure refrigerant connection pipe 540. At this time, the flow rate of the refrigerant passing through the first liquid refrigerant pipe 610a is regulated by the first flow control valve 130. In addition, the flow rate of the liquid refrigerant flowing out from the liquid refrigerant outlet port 670c of the gas-liquid separator 670 is also regulated by the third flow control valve 680.

By flowing the refrigerant in this manner, the first heat exchanger 110 functions as a refrigerant evaporator, and the second heat exchanger 210 functions as a refrigerant condenser. As a result, the air supply unit 100 cools the supply air SA blown by the first fan 120 in the first heat exchanger 110 and then releases it into the target space S. In addition, the exhaust unit 200 heats the return air RA blown by the second fan 220 in the second heat exchanger 210 and then releases it outside the target space S as exhaust air EA. Heating the return air RA by the exhaust unit 200 corresponds to heat recovery from the return air RA.

(3-1-3) Flow path switching unit 600a and pair 400 of air supply unit 100 and exhaust unit 200 performing heating operation
For the pair 400 for which it has determined that heating operation should be performed (pair 400a and pair 400c in FIG. 10B ), the control unit 700a opens the corresponding first high-pressure gas refrigerant control valve 631a, closes the corresponding first low-pressure gas refrigerant control valve 632a, closes the corresponding second high-pressure gas refrigerant control valve 661a, and opens the corresponding second low-pressure gas refrigerant control valve 662a. Additionally, the control unit 700a controls the rotation speeds of the first fan 120 and the second fan 220 and adjusts the apertures of the first flow rate control valve 130, the second flow rate control valve 230, and the third flow rate control valve 680 so that appropriate operating conditions are achieved based on the measurement values of the sensors 140, 240, 380, the set temperatures, and the like (for example, so that one or more of the evaporation temperature, condensation temperature, degree of subcooling, degree of superheat, etc., reach target values).

As a result, the refrigerant that flows from the high-pressure refrigerant communication pipe 550 into the gas-liquid separator 670 passes through the gas refrigerant outflow port 670b, the first high/low pressure gas refrigerant pipe 621a, the first combined gas refrigerant pipe 623a, the first heat exchanger 110, and the first liquid refrigerant pipe 610a, in that order. At this time, the flow rate of the refrigerant passing through the first liquid refrigerant pipe 610a is regulated by the first flow control valve 130.

The refrigerant flowing out of the first liquid refrigerant pipe 610a, together with the refrigerant flowing out of the liquid refrigerant outlet port 670c of the gas-liquid separator 670, passes through the second liquid refrigerant pipe 640a, the second heat exchanger 210, the second combined gas refrigerant pipe 653a, and the second low-pressure gas refrigerant pipe 652a, in that order, before flowing into the low-pressure refrigerant connection pipe 540. At this time, the flow rate of the refrigerant passing through the second liquid refrigerant pipe 640a is regulated by the second flow control valve 230. In addition, the flow rate of the liquid refrigerant flowing out of the liquid refrigerant outlet port 670c of the gas-liquid separator 670 is also regulated by the third flow control valve 680.

By flowing the refrigerant in this manner, the first heat exchanger 110 functions as a refrigerant condenser, and the second heat exchanger 210 functions as a refrigerant evaporator. As a result, the air supply unit 100 heats the supply air SA blown by the first fan 120 in the first heat exchanger 110 and then releases it into the target space S. In addition, the exhaust unit 200 cools the return air RA blown by the second fan 220 in the second heat exchanger 210 and then releases it outside the target space S as exhaust air EA. The cooling of the return air RA by the exhaust unit 200 corresponds to heat recovery from the return air RA.

(3-1-4) Pair 400 of air supply unit 100 and exhaust unit 200 that does not perform temperature adjustment operation
Although not shown in the figure, for pairs 400 for which the control unit 700a has determined that temperature adjustment operation will not be performed, the first high-pressure gas refrigerant control valve 631a, the first low-pressure gas refrigerant control valve 632a, the second high-pressure gas refrigerant control valve 661a, and the second low-pressure gas refrigerant control valve 662a are all closed.

As a result, the refrigerant that flows from the high-pressure refrigerant communication pipe 550 into the gas-liquid separator 670 is restricted from flowing into the air supply unit 100 and the exhaust unit 200. As a result, the first heat exchanger 110 and the second heat exchanger 210 are restricted from functioning as heat exchangers.

(3-1-5) Compressor unit 300 in the third heat exchanger function state
When the control unit 700a determines that the refrigerant circuit 500a should be in the third heat exchanger function state, it switches the third control valve 360a, which is in the closed state, to the open state, closes the fourth control valve 390a, which is in the open state, and begins controlling the rotation speed of the third fan 320.

When the third control valve 360a is open and the fourth control valve 390 is closed, the refrigerant flowing through the discharge pipe 332 passes through the first port 370aa of the four-way switching valve 370a, the fourth port 370ad of the four-way switching valve 370a, the third control valve 360a, the third heat exchanger 310a, and the second check valve 352a, in that order, before flowing into the high-pressure refrigerant communication pipe 550. Because the fourth control valve 390 is closed, the passage of refrigerant through the fourth control valve 390 is restricted. The control unit 700 then begins controlling the rotation speed of the third fan 320 to achieve appropriate operating conditions (e.g., so that one or more of the evaporation temperature, condensation temperature, degree of subcooling, degree of superheat, etc., reach their target values) based on the measurement values of the sensors 140, 240, and 380, the set temperature, etc.

By allowing the refrigerant to flow in this manner, the third heat exchanger 310a functions as a refrigerant condenser. As a result, even if fluctuations in the outside air OA and return air RA cause an increase in the heat load of the first heat exchanger 110, which functions as an evaporator, the third heat exchanger 310 compensates for the capacity of the second heat exchanger 210, which functions as a condenser. Therefore, the ventilator 1 can perform stable temperature regulation.

(4) Modifications (4-1) Modification 2A
The control unit 700a may set the refrigerant circuit 500a in the third heat exchanger function state when the four-way switching valve 370a is in the second state. Fig. 12 is a refrigerant circuit diagram in the third heat exchanger function state when the four-way switching valve 370a is in the second state.

In this case, when the third control valve 360a is open and the fourth control valve 390 is closed, the compressor 330 draws refrigerant from the low-pressure refrigerant communication pipe 540 through the fourth check valve 354a, the third heat exchanger 310a, the third control valve 360a, the fourth port 370ad of the four-way switching valve 370a, and the third port 370ac of the four-way switching valve 370a into the suction pipe 331a and discharges it as high-pressure refrigerant from the discharge pipe 332. The refrigerant compressed to high pressure by the compressor 330a passes through the discharge pipe 332a, the second port 370ab of the four-way switching valve 370a, the first port 370aa of the four-way switching valve 370a, and the third check valve 353a, in that order, before flowing into the high-pressure refrigerant communication pipe 550.

By allowing the refrigerant to flow in this manner, the third heat exchanger 310a functions as an evaporator for the refrigerant. As a result, even if fluctuations in the outside air OA and return air RA cause an increase in the heat load on the first heat exchanger 110, which functions as a condenser, the third heat exchanger 310 compensates for the capacity of the second heat exchanger 210, which functions as an evaporator. Therefore, the ventilator 1 can perform stable temperature adjustment.

<Conclusion>
Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as defined in the claims.

1, 1a: Ventilation device 100: Air supply unit (first unit)
110: First heat exchanger 120: First fan 200: Exhaust unit (second unit)
210: Second heat exchanger 220: Second fan 310, 310a: Third heat exchanger 320: Third fan 330, 330a: Compressor 360, 360a: Third control valve (flow path adjustment mechanism)
390: Fourth control valve (flow path adjustment mechanism)
500, 500a: refrigerant circuit 700, 700a: control unit OA: outside air S: target space

Japanese Patent Application Laid-Open No. 2023-051676

Claims (8)

A ventilation device (1, 1a) for ventilating air in a target space (S),
a refrigerant circuit (500) to which a compressor (330, 330a), a first heat exchanger (110) , a second heat exchanger (210) , and a third heat exchanger (310, 310a) are connected and which is filled with a refrigerant;
a first fan (120) that discharges outside air (OA), which is air outside the target space (S), into the target space (S) through the first heat exchanger (110);
a second fan (220) that discharges the air in the target space (S) to the outside of the target space (S) through the second heat exchanger (210);
a flow path adjustment mechanism (360, 360a, 390) that adjusts a flow path of the refrigerant flowing through the refrigerant circuit (500) between a first state that restricts the inflow of the refrigerant into the third heat exchanger (310, 310a) and a second state that allows the inflow of the refrigerant into the third heat exchanger (310, 310a);
a control unit (700) that controls the flow path adjustment mechanisms (360, 360a, 390);
a first unit (100) having the first heat exchanger (110) and the first fan (120);
a second unit (200) having the second heat exchanger (210) and the second fan (220);
Equipped with
The third heat exchanger (310, 310a)
heat exchange between the refrigerant and a heat medium other than the refrigerant ;
The control unit (700)
adjusting the flow path by the flow path adjustment mechanism (360, 360a, 390) in accordance with the heat load of the first heat exchanger (110) or the second heat exchanger (210);
Ventilation device (1, 1a). The control unit (700, 700a)
determining whether the refrigerant in the refrigerant circuit is in a first refrigerant state based on the pressure (Ps) or the temperature (Te) of the refrigerant in the refrigerant circuit;
When it is determined that the refrigerant in the refrigerant circuit is in the first refrigerant state, the flow path adjustment mechanism is set to the second state;
When it is determined that the refrigerant in the refrigerant circuit is not in the first refrigerant state, the flow path adjustment mechanism is controlled to be in the first state.
A ventilation device (1, 1a) according to claim 1 . The system further includes a third fan (320) that blows air to the third heat exchanger (310, 310a),
The control unit (700, 700a)
determining whether the refrigerant in the refrigerant circuit is in a first refrigerant state based on the pressure (Ps) or the temperature (Te) of the refrigerant in the refrigerant circuit;
When it is determined that the refrigerant in the refrigerant circuit is in the first refrigerant state, the third fan is operated;
When it is determined that the refrigerant in the refrigerant circuit is not in the first refrigerant state, the third fan is stopped.
A ventilation device (1, 1a) according to claim 2 . The system further includes a third fan (320) that blows air to the third heat exchanger (310, 310a),
The third heat exchanger (310, 310a), the third fan (320), and the compressor (330)
Housed in a single housing,
A ventilation device (1, 1a) according to claim 1. The third heat exchanger (310, 310a) is installed outside the target space (S).
A ventilation device (1, 1a) according to claim 1. The heat transfer medium is
The outside air (OA),
A ventilation device (1, 1a) according to claim 1. The third heat exchanger (310, 310a)
When the second heat exchanger (210) functions as an evaporator, it functions as an evaporator;
The second heat exchanger (210) functions as a condenser when the second heat exchanger (210) functions as a condenser.
A ventilation device (1, 1a) according to claim 1. The number of the first units is one and the number of the second units is two or more, or
the number of the first units is two or more, and the number of the second units is one;
10. The ventilation device of claim 1.